Nuclear Magnetic Resonance (NMR) has been used for testing for the presence of various components in substances, including testing of consumables such as food and beverages in closed containers. See, e.g., U.S. Pat. Nos. 6,911,822, 7,012,427, and 7,339,377. Other patents relevant to NMR testing of substances to determine the presence of various components include U.S. Pat. Nos. 3,975,675, 4,045,723, 4,550,082, 5,270,650, 5,530,353, 5,811,305, 6,333,629, 6,462,546, and 6,806,090. Non-patent references include Weekley, A. J., et al., “Using NMR to Study Full Intact Wine Bottles,” J. Magn. Reson., 161:91-98 (2003); Sobieski. D. N., et al., “Towards Rapid Throughput NMR Studies of full Wine Bottles,” Solid State NMR, 29:67-74 (2006); Drysdale and Fleet “Acetic Acid Bacteria in Winemaking: A Review” Am. J. Enol. Vitic. 39:143-154 (1988); Castilieira et al. “Simultaneous Determination of Organic Acids in Wine Samples by Capillary Electrophoresis and UV Detection: Optimization with Five Different Background Electrolytes” J. High Resol. Chromatogr. 23:647-652 (2000); Guillou and Reniero “Magnetic Resonance Out Bad Wine” Physics World 11:22-23 (1998); Hayes et al. “An Efficient, Homogeneous Radiofrequency Coil for Whole-Body NMR Imaging at 1.5 T” J. Magn. Reson. 63:622-628 (1985); Schindler et al. “A Rapid Automated Method for Wine Analysis Based Upon Sequential Injection (SI)-FTIR spectroscopy” Fresenius 362:130-136 (1998); Weekley, A. J., Bruins, P. And Augustine, M. P., “Nondestructive Method Of Determining Acetic Acid Spoilage In An Unopened Bottle Of Wine” American Journal Of Enology And Viticulture, Vol. 53, December 2002 (2002-12), Pages 318-321; Mccarthy And Kauten Magnetic Resonance Imaging Applications In Food Research “Trends In Food Science And Technology, 1990, Pages 134-139; Schmidt, Sun And Litchfield, Applications Of Magnetic Resonance Imaging In Food Science” Critical Reviews In Food Science And Nutrition, Vol. 36, No. 4, 1996, pages 357-385.
There is a prevailing operational need for a unified, cost-effective approach to the detection of liquid explosive threats in the civil aviation industry as well as other mass transportation modes, such as a tabletop Bottled Liquid Scanner (BLS) that is capable of detecting and distinguishing threat liquids from benign liquids in unopened/sealed Stream-of-Commerce (SOC) containers including non-ferrous metal containers.
Nuclear relaxometry methods at ultra-low fields (ULF) using extremely sensitive sensors haven been used to measure relaxation parameters that enable the gross differentiation of liquids. Relaxation time data set pairs (denoted T1 and T2) can be used to generally characterize certain (protonated) liquids.
Several significant technical issues remain to be resolved with low-field relaxometry approaches, including accurate, high-confidence identification the wide range of liquids expected to be encountered in a TSA checkpoint environment. Nuclear relaxation data alone (e.g. T1 and T2) are inherently ambiguous and generally do not offer highly accurate liquids identification. Cost, physical footprint, and compatibility with TSA CONOPS are also issues requiring further resolution with low-field relaxation approaches.
While nuclear relaxation data, is useful for gross-order characterization of certain liquids, it is insufficient for complete and unambiguous determination of threat vs. benign liquids. At least two published theoretical investigations Mauler, J., et al, Identification of Liquids Encountered in Carry-on-Luggage by Mobile NMR, Springer Science and Business Media B.V., p. 193, 2009, and Kumar, S., et al, Screening sealed bottles for liquid explosives, SPIE Vol. 2934, pp. 126, 1997, have shown that relaxation data, if used alone, is indeterminate as to exact liquid identification. Mauler concludes that “Identifying liquids based on relaxation data is possible only with certain restrictions, for instance the number of liquids must be limited” (p. 203), and Kumar asserts (p. 126) that “An ideal system would use high-resolution MR spectroscopy capable of resolving chemical shift spectra to distinguish all liquids with complete reliability.” In light of the fact that the variety of known threat liquids and liquid-powder threat mixtures numbers in the hundreds, and that the total number of liquids/liquid mixtures challenging a screening checkpoint potentially numbers in the tens of thousands, this prior research indicates that a robust technology capable of accurate liquids identification over a large range of categories must be developed and employed.
Additionally, liquid samples can be altered, potentially causing the current generation of relaxation technology to be deliberately “spoofed”, allowing threat liquids to be masked as benign materials. Recent research conducted by the inventor hereof has shown that a variety of threat liquids can be cloaked or and made to resemble benign liquids (e.g. water) with respect to their relaxation behavior. Physical-chemical properties can be similarly altered and do not offer a unique “fingerprint” for accurate; high-confidence liquids identification. These findings impact the efficacy of the current generation of low-field relaxometry technology as a security screening instrument, unless a discriminating liquid parameter can be found.
Furthermore, the low magnetic fields employed require significant instrument shielding in order to be unperturbed by simple background magnetic interference, such as the Earth's magnetic field. This shielding increases the instrument's physical footprint and cost, and also creates certain operator limitations and restrictions that are difficult to practically achieve in an airport setting (airports are inherently “noisy” magnetic field environments). Devices employed in many low-field systems must be cooled to within a few degrees of absolute zero which requires frequent charging and filling with liquid helium—an added operational expense and logistical challenge. In addition, system stability, instrument drift and other calibration issues have been encountered during the development of low field relaxometry methods.
All publications referred to herein are incorporated herein by reference to the extent not inconsistent herewith.
Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent.